Nutrition is a central public health concern in the twenty-first century. Previous international research in nutrition was primarily descriptive epidemiology and included large-scale intervention ...trials. There has been insufficient attention to the mechanisms by which nutrient supplements appear to reduce mortality and little specificity in application and delineation of the forms of a specific nutrient to maximize benefits and minimize adverse affects and on the effect of nutrient combinations. After the dramatic success of the green revolution, agricultural research support was reduced despite an expanding world population and an increasing need for agricultural products. The potential of molecular genetics to improve food quality, specific nutrient content, and yield and disease resistance has just begun to be explored. In addition, the development of edible vaccines as a way to immunize a greater proportion of the world's children is a highly desirable goal and is achievable with sufficient resources.
The ability of an individual to mount defense responses to infection depend in part on the capacity to produce cytokines such as interleukin 1 (IL-1) and tumor necrosis factor (TNF). The specialized ...equipment, labor intensity, and sterile practice required for the standard in vitro evaluation of cytokine production can make such evaluation impractical in some clinical situations. We report a method for stimulating whole blood to produce cytokines that can be implemented in laboratories without tissue culture facilities and requires minimal sample preparation. IL-1 beta and TNF alpha production in whole blood samples was stimulated with endotoxin and/or phytohemagglutinin in standard EDTA-containing vacuum collection tubes. After incubation, plasma was removed and frozen for later assay. Comparison of this whole blood method with isolated mononuclear cell cultures indicated a significant correlation for IL-1 beta production (r = 0.746, P = 0.005). This technique also produced the newly described cytokine, IL-1 receptor antagonist. We conclude that the whole blood method is an acceptable alternative to isolated cell culture methods for measuring IL-1 beta in situations that preclude the standard in vitro approach.
We have determined the nucleotide sequence of the sltA and sltB genes that encode the Shiga-like toxin (SLT) produced by Escherichia coli phage H19B. The amino acid composition of the A and B ...subunits of SLT is very similar to that previously established for Shiga toxin from Shigella dysenteriae 1, and the deduced amino acid sequence of the B subunit of SLT is identical with that reported for the B subunit of Shiga toxin. The genes for the A and B subunits of SLT apparently constitute an operon, with only 12 nucleotides separating the coding regions. There is a 21-base-pair region of dyad symmetry overlapping the proposed promoter of the slt operon that may be involved in regulation of SLT production by iron. The peptide sequence of the A subunit of SLT is homologous to the A subunit of the plant toxin ricin, providing evidence for the hypothesis that certain prokaryotic toxins may be evolutionarily related to eukaryotic enzymes.
To examine the reported heterogeneity of endothelial cells to Shiga-like toxin 1 (Stxl), the responses of human umbilical (HUVEC) and saphenous (HSVEC) vein endothelial cells to cytokines, butyrate, ...and toxin were compared. Untreated HSVEC were generally more susceptible than were HUVEC to Stxl; pretreatment of either cell with lipopolysaccharide, interleukin-1β, or tumor necrosis factor-α enhanced Stxl toxicity. Dexamethasone alone increased total globotriaosylceramide (Gb3) content and toxin binding but inhibited cytokine-enhanced cytotoxicity, whereas the differentiation agent, sodium butyrate, increased both Gb3 content and cytotoxicity responses to Stxl, most prominently in HSVEC. Stxl toxicity directly correlated with the release of von Willebrand factor from HSVEC but not from HUVEC. Thus, HUVEC and HSVEC exhibit distinctive responses to Stxl, cytokines, and butyrate. This suggests the need for caution in extrapolating from in vitro studies utilizing one endothelial cell type to in vivo events during pathogenesis of Stxmediated thrombotic microangiopathies.
Adult Macaca radiata (n=22) were infected intragastrically with 1012 Escherichia coli O157:H7 strain 84-01, which produces Shiga toxins 1 and 2. Clinical symptoms and bacterial excretion were ...documented in each monkey for a specified time period before they were killed. At necropsy, samples were obtained for culture and histologic and ultrastructural examination. Seventeen monkeys had diarrhea: E. coli O157 was isolated from postinfection stool samples from all monkeys and from autopsy cultures for 14 of 22 monkeys. Histologic examination showed attaching-effacing lesions, which appeared at 12 h and persisted for 7 days, in 12 monkeys. Widening of the intercellular spaces, degeneration and vacuolization of the epithelial cells, epithelial tufting, extrusion of epithelial cells, and neutrophilic infiltration were characteristic features seen in 20 of the 22 infected monkeys but not in 4 control monkeys. This monkey model closely parallels the early stages of the disease produced by E. coli O157:H7 and would be useful in the further study of pathogenic mechanisms and prevention methods in enterohemorrhagic E. coli infections
To examine the relation of circulating cytokines and cytokine antagonists to the progression of human immunodeficiency virus type 1 (HIV-1) disease.
Cross-sectional analysis.
An ambulatory acquired ...immunodeficiency syndrome (AIDS) research clinic in Kinshasa, Zaire.
48 women with AIDS, 51 women with HIV infection who were clinically asymptomatic, and 11 female controls who did not have HIV infection, all from Zaire.
Plasma levels of interleukin-1beta, tumor necrosis factor-alpha (TNF-alpha), interleukin-6, interleukin-8, interferon-gamma, interleukin-1beta receptor antagonist (interleukin-1Ra), and TNF soluble receptor p55 (TNFsRp55) were assayed by specific radioimmunoassays. Plasma levels of interferon-gamma were assayed by commercial enzyme-linked immunosorbent assay. The Wilcoxon rank-sum test was used to assess the significance of mean and median differences between groups.
Of the 48 patients with AIDS, circulating interleukin-1beta was detected in 2, TNF-alpha in 4, interleukin-6 in 3, and interleukin-8 in 12. None of these factors were seen in any of the 11 controls. Median values of interleukin-1beta (320 pg/mL), TNF-alpha (210 pg/mL), and interleukin-8 (750 pg/mL) were elevated in HIV-infected asymptomatic patients compared with patients with AIDS (2-, 2.6-, and 18.7-fold higher, respectively; P < 0.001). Interleukin-1Ra and TNFsRp55 levels were substantially higher than interleukin-1beta and TNF-alpha levels in HIV-infected asymptomatic patients (73- and 14-fold, respectively) and were higher than those in patients with AIDS (17.8- and 1.74-fold, respectively).
High circulating levels of the proinflammatory cytokines interleukin-1beta and TNF-alpha, combined with an excess of their natural inhibitors interleukin-1Ra and TNF-sRp55, were seen in clinically asymptomatic HIV-1-positive African women but not in African women with AIDS or in HIV-negative controls. Circulating cytokine antagonists may play a clinical role in modulating cytokine-associated symptoms in the early phases of HIV infection.
We reexamined the binding specificity of the Shiga-like toxin variant associated with porcine edema disease, SLT2e, which is reported to be more cytotoxic for Vero cells than for HeLa cells, by using ...receptor-deficient cells and a liposomal insertion system for purified glycolipids. We found that SLT2e preferentially uses globotetraosylceramide as a receptor but can also cause cytotoxicity by using globotriaosylceramide, the SLT2 receptor. We conclude that the differential cytotoxicity of SLT2e on HeLa and Vero cells is a function of both the receptor preference of the toxin and the specific glycolipid content of the target cells being used
Differentiated villus intestinal epithelial cells express globotriaosylceramide, the Shiga-like toxin 1 (SLT-1) receptor, and are sensitive to toxin-mediated cytotoxicity, whereas undifferentiated ...crypt cells neither express Gb3 nor respond to toxin. To investigate if SLT-1 receptors are maturationally regulated in human intestinal cells, we examined the effect of butyrate, a known transcriptional regulator of differentiation genes in many cell types, using cultured colonic cancer-derived epithelial cell lines. Exposure to butyrate increased villus cell marker enzymes such as alkaline phosphatase, sucrase, and lactase, expression of toxin receptors, and sensitivity to SLT-1 in villus-like CaCo-2A and HT-29 cells. These effects were reversibly inhibited by preincubation of CaCo-2A cells with actinomycin D or cycloheximide. Butyrate-treated CaCo-2A cells unable to bind fluoresceinated SLT-1 B subunit were undifferentiated as assessed by alkaline phosphatase activity. HT-29 cells induced to differentiate by another signal, glucose deprivation, upregulated receptor content and response to toxin. Crypt-like T-84 cells responded to butyrate with a modest increase in alkaline phosphatase and toxin binding, but no induction of sucrase or lactase, and no change in sensitivity to toxin. The results demonstrate that expression of SLT-1 toxin receptors and toxin sensitivity are coregulated with cellular differentiation in cultured intestinal cells.
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